Polishing composition and method of preparing same



Patented Feb. 7, 1933 UNITED STATES PATENT OFFICE MISSOURI, ASSIGNORS TO SWANN RESEARCH, INC., A CORPORATION OF ALABAMA POLISHING COMPOSITION AND METHOD OF PREPARING SALIE No Drawing.

This invention relates to polishing bases and in particular to a dicalcium phosphate polishing base.

The object of this invention is to produce a dry polishing base composed of hydrated or partially dehydrated dicalcium phosphate dihydrate. Another object is to produce a dicalcium phosphate polishing base of low abrading power.

-Hitherto it has been extremely difiicult to produce a polishing base of uniform finely divided particles sufficiently soft so that surfaces which were polished therewith would not be excessively abraded. At the same time it was desirable that the particles of the polishing base be of suflicient hardness so that a polishing effect could be obtained without the expenditure of too much effort. We have now discovered that a polishing base comprising partially dehydrated dicalcium phosphate dihydrate which has been prepared according to the method herein described has a very low abrading power combined with sufiicient hardness so that a good polish may i be obtained.

Measurement of the abrading power of polishing agents consists merely in comparing the weight of material removed from a reference substance by means of various polishing agents applied under controlled conditions. Experiments whichwe have made to compare the abrading power of the herein described partially dehydrated dicalcium phosphate dihydrate with anhydrous dicalcium phosphate have shown that the former has only 1/10 to 1/30 of the abrading power of the latter.

The material herein described may be used as a metal polish or for lacquered or plated surfaces, especially on automobiles, as a jewelers olish or as a dentifrice base.

We ave discovered that by controlling the conditions under which dicalcium phosphate is formed we are enabled to produce a dry,

hydrated or partially dehydrated dicalcium phosphate dihydrate of low abrading power suitable for use as or for introduction into polishing compositions. We havev further discovered that by the addition of aluminum phosphate or aluminum hydrate into the Serial No. 541,950.

reaction mixture in which precipitated dicalcium phosphate is being formed, the production of the dry dicalciumjphosphate in a hydrated or partially dehydrated form with a low degree of abrading power is rendered extremely simple.

The addition of aluminum hydrate into the reacting mass causes the formation of phosphate of aluminum, hence we may add this aluminum compound directly into the reacting mixture or may form it by reaction of the hydrate and phosphoric acid.

Our new product may be usedin the dry PAUL LOGUE, OF BIRMINGHAM, ALABAMA, AND THEODORE W. SCHILB, OR ST. LOUIS,

for lacquered surfaces for which purpose it v is mixed with sufiicient water to form a paste to which a small amount of soap may 'be added if desired.

The following examples illustrate our method of preparing a polishing base composed of hydrated or only partly dehydrated dicalcium phosphate oflow polishing power.

Example I filter cake will contain approximately 30% excess moisture. The filter cake is now dried .at a temperature of C. The drying operation is preferablycarried out in a vacuum with stirring until a sample of the product shows an ignition loss of 14-21 per cent of moisture. When this degree of drying has been obtained, the product is ground to a fine powder and is suitable for incorporation into a polish in the usual manner.

Example H tion of the lime and phosphoric acid, the temperature is maintained below C. in order to assure the formation of the hydrated dicalcium phosphate.- After reaction the slurry containing the precipitated dicalcium phosphate and aluminum phosphate is filtered. The cake is now dried, in this case however, because of the protecting action of the aluminum phosphate in the cake, the temperature may be increased to 104 C. without any danger of forming the anhydrous dicalcium phosphate. Drying, which may or may not be carried out in a vacuum, and is preferably done with stirring, is continued until the product shows an ignition loss of between 14 and 21 per cent.

Some variations may be made in the amount of aluminum phosphate or hydrate added; however, it is desirable to keep the content of aluminum phosphate between 1 and 3 per cent if a higher drying temperature than C. is emp oyed. As pointed out above, when 3 per cent of aluminum phos-.

phate is present in the product a maximum temperature of 104 C. is permissible, during drying; when less than this amount is present t 0 temperature of drying is decreased so that a product having a low abrading power is obtained. perature permissible during drying of the dicalcium phosphate in the absence of any aluminum phosphate is in the neighborhood of 80 C.

. The ignition loss by weight. It is determined by heating a two-gram sampleat a temperature of 800 C. for 30 minutes or until constant weight is obtained.

A dried product made in the above manner and having an ignition loss of substantially less than 21% will comprise partially dehydrated dicalcium phosphate dihydrate. The abrading power of this product, however, will not be appreciably hi her because of the presence 0 The maximum temthis partia y dehydrated dical cium phosphate, if the procedure given above is carefully followed.

While we have described our invention in but two forms, it will be obvious to those sllilled in the art that it is not so limited, but

is susceptible of various other changes and modifications, without departing from the spirit thereof, and We desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What We claim is:

1. A polishing base comprising dicalcium phosphate dihydrate which. has been partially dehydrated and a relatively small amount of aluminum phosphate.

2. A. polishing base comprising dicalcium phosphate dihydrate which has been partially dehydrated and containing from 1 to 3 per cent of aluminum phosphate. 7

3. A polishing base composed of dicalcium phosphate dihydrate having a low abrading power and which has been dehydrated until it has an ignition loss of between 14 and 21 per cent, and suflicient aluminum phosphate to raise the drying temperature of the product slightly above normal temperature.

i In testimony whereof 'we aflix our signatures.

PAUL LOGUE.

THEODORE W. SCHILB.

loo

of the product is preferably maintained between 14 and 21 per cent 

